around for a long time
- association proxy now returns None for proxied scalar that is also None, rather
than raising AttributeError. [ticket:2810]

- rework the event system so that event modules load after their
targets, dependencies are reversed
- create an improved strategy lookup system for the ORM
- rework the ORM to have very few import cycles
- move out "importlater" to just util.dependency
- other tricks to cross-populate modules in as clear a way as possible

if the given target/event/fn is set up to listen.
- repair mutable package which is doing some conditional event listening

that ``discriminator_on_association.py`` makes use of single table
inheritance do the work with the "discriminator".  Also
added a true "generic foreign key" example, which works similarly
to other popular frameworks in that it uses an open-ended integer
to point to any other table, foregoing traditional referential
integrity.  While we don't recommend this pattern, information wants
to be free.  Also in 0.8.3.

- Added a convenience class decorator :func:`.as_declarative`, is
a wrapper for :func:`.declarative_base` which allows an existing base
class to be applied using a nifty class-decorated approach.  Also
in 0.8.3.

:meth:`.Insert.from_select`.  Given a list of columns and
a selectable, renders ``INSERT INTO (table) (columns) SELECT ..``.
While this feature is highlighted as part of 0.9 it is also
backported to 0.8.3. [ticket:722]
- The :func:`.update`, :func:`.insert`, and :func:`.delete` constructs
will now interpret ORM entities as FROM clauses to be operated upon,
in the same way that select() already does.  Also in 0.8.3.

by name in a string argument used with ``order_by``,
``primaryjoin``, or similar in :func:`.relationship`,
in addition to column-bound attributes. [ticket:2761]

- simplify